Post-landing major element quantification using SuperCam laser induced breakdown spectroscopy

• Published in: Spectrochimica acta. Part B: Atomic spectroscopy Vol. 188; p. 106347
• Main Authors: Anderson, Ryan B., Forni, Olivier, Cousin, Agnes, Wiens, Roger C., Clegg, Samuel M., Frydenvang, Jens, Gabriel, Travis S.J., Ollila, Ann, Schröder, Susanne, Beyssac, Olivier, Gibbons, Erin, Vogt, David S., Clavé, Elise, Manrique, Jose-Antonio, Legett, Carey, Pilleri, Paolo, Newell, Raymond T., Sarrao, Joseph, Maurice, Sylvestre, Arana, Gorka, Benzerara, Karim, Bernardi, Pernelle, Bernard, Sylvain, Bousquet, Bruno, Brown, Adrian J., Alvarez-Llamas, César, Chide, Baptiste, Cloutis, Edward, Comellas, Jade, Connell, Stephanie, Dehouck, Erwin, Delapp, Dorothea M., Essunfeld, Ari, Fabre, Cecile, Fouchet, Thierry, Garcia-Florentino, Cristina, García-Gómez, Laura, Gasda, Patrick, Gasnault, Olivier, Hausrath, Elisabeth M., Lanza, Nina L., Laserna, Javier, Lasue, Jeremie, Lopez, Guillermo, Madariaga, Juan Manuel, Mandon, Lucia, Mangold, Nicolas, Meslin, Pierre-Yves, Nelson, Anthony E., Newsom, Horton, Reyes-Newell, Adriana L., Robinson, Scott, Rull, Fernando, Sharma, Shiv, Simon, Justin I., Sobron, Pablo, Fernandez, Imanol Torre, Udry, Arya, Venhaus, Dawn, McLennan, Scott M., Morris, Richard V., Ehlmann, Bethany
• Format: Journal Article
• Language: English
• Published: Johnson Space Center Elsevier B.V 01.02.2022; Science Direct; Elsevier BV; Elsevier
• Subjects: Ablation; Aluminum oxide; Analytical methods; Calibration; Carbonates; Chemical composition; Chemometrics; Distance; Geology; Geosciences (General); INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Laser induced breakdown spectroscopy; Lasers; LIBS; Manganese; Mars; Mars craters; Mars landing; Mars rovers; Minerals; Multivariate regression; Oxides; Regression; Regression analysis; Regression models; Sciences of the Universe; Silica; Silicates; Silicon dioxide; Sodalite; Spectra; Spectroscopy; Spectrum analysis; Test sets; Titanium dioxide; Mars; Laser induced breakdown spectroscopy; Regression; Multivariate regression; Calibration; LIBS; Chemometrics; Supercam; Mars 2020; Libs
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/j.sab.2021.106347

The SuperCam instrument on the Perseverance Mars 2020 rover uses a pulsed 1064 nm laser to ablate targets at a distance and conduct laser induced breakdown spectroscopy (LIBS) by analyzing the light from the resulting plasma. SuperCam LIBS spectra are preprocessed to remove ambient light, noise, and the continuum signal present in LIBS observations. Prior to quantification, spectra are masked to remove noisier spectrometer regions and spectra are normalized to minimize signal fluctuations and effects of target distance. In some cases, the spectra are also standardized or binned prior to quantification. To determine quantitative elemental compositions of diverse geologic materials at Jezero crater, Mars, we use a suite of 1198 laboratory spectra of 334 well-characterized reference samples. The samples were selected to span a wide range of compositions and include typical silicate rocks, pure minerals (e.g., silicates, sulfates, carbonates, oxides), more unusual compositions (e.g., Mn ore and sodalite), and replicates of the sintered SuperCam calibration targets (SCCTs) onboard the rover. For each major element (SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O, K2O), the database was subdivided into five “folds” with similar distributions of the element of interest. One fold was held out as an independent test set, and the remaining four folds were used to optimize multivariate regression models relating the spectrum to the composition. We considered a variety of models, and selected several for further investigation for each element, based primarily on the root mean squared error of prediction (RMSEP) on the test set, when analyzed at 3 m. In cases with several models of comparable performance at 3 m, we incorporated the SCCT performance at different distances to choose the preferred model. Shortly after landing on Mars and collecting initial spectra of geologic targets, we selected one model per element. Subsequently, with additional data from geologic targets, some models were revised to ensure results that are more consistent with geochemical constraints. The calibration discussed here is a snapshot of an ongoing effort to deliver the most accurate chemical compositions with SuperCam LIBS. [Display omitted] •We quantify the following oxides: SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O, K2O.•Multivariate regression models were trained on a diverse suite of spectra.•Of the algorithms considered, ensemble methods performed well but had limitations.•We evaluated models based on laboratory and Mars results.•Work is ongoing to improve major element results and quantify additional elements.